长江口盐沼带湿地生态演替过程中甲烷排放研究

Methane emission in the process of wetland vegetation succession in salt marsh of Yangtze River estuary

甲烷(CH4)作为河口湿地碳循环的重要中间产物,是大气中仅次于二氧化碳(CO2)的第二大温室气体,其排放清单对于全球气候变暖趋势的预测具有重要意义.因此,本研究采用静态箱-气相色谱技术,针对长江口盐沼带湿地CH4的排放通量展开了为期2年、每月1次的现场观测.研究结果表明,长江口盐沼带湿地持续表现为大气CH4的净排放源,其中,2011年在海三棱藨草覆盖情况下,全年CH4平均排放通量达到了1.00 mg·m-2·h-1,2012年互花米草大规模入侵后,海三棱藨草生物量显著减小,全年CH4排放通量减小为0.55 mg·m-2·h-1.Pearson相关性分析表明,沉积物有机碳含量、光合有效辐射及含水率等均不是影响长江口盐沼带湿地CH4排放的重要环境因子.在2011年,海三棱藨草生物量(p=0.001,r=0.928)、气温(p<0.01,r=0.432)均与CH4排放通量呈现显著正相关,全年CH4最大排放通量出现在生物量最大的夏季8月份;2012年随着互花米草的入侵,CH4排放通量在5月份达到了最大值,自5月份之后逐渐减小,互花米草的入侵使长江口中潮滩盐沼带湿地CH4排放通量整体呈现出了下降的趋势.

As important intermediates in the process of carbon cycle in estuarine wetlands,methane( CH4) is the important greenhouse gas that only seconds to carbon dioxide( CO2) in the atmosphere. Accurate estimation of CH4emission inventory is important in predicting the global warming tendency. The static closed chamber-chromatograph method was used to investigate the monthly CH4fluxes from February 2011 to December 2012 in the salt marshes of Yangtze River estuary. The results indicated that salt marshes in Yangtze River estuary acted as a net source of atmospheric CH4and the annual average CH4fluxes was 1. 00 mg·m-2·h-1in 2011 when the Scirpus mariqueter was the dominant species. After the full-scale invasion of the alien Spartina alterniflora,biomass of Scirpus mariqueter decreased greatly in 2012,with the annual average CH4fluxes decreased to 0. 55 mg·m-2·h-1.According to Pearson correlation analysis,sediment organic carbon,solar radiation and the water content were not the main factors of CH4fluxes. In addition,CH4fluxes were significantly positively correlated with both aboveground biomass of Scirpus mariqueter( p = 0. 001,r = 0. 928) and temperature( p<0. 01,r = 0. 432) in 2011. Along with the invasion of Spartina alterniflora in 2012,CH4fluxes reached the highest value in May. The total CH4emissions also decreased significantly due to the invasion of Spartina alterniflora in 2012.